Urinary incontinence, which is a condition involving involuntary loss of urine, is a problem with millions of people. It is much more prevalent among women than men. In some patients, loss of urine is associated with transient increases in intra-abdominal pressure that result from activities such as coughing, sneezing, lifting, straining, exercise and in severe cases, even simply changing body position. This is called stress incontinence.
The normal urinary continence mechanism combines contributions from several components including muscles in and around the urethra, blood pressure in the urethral vascular plexus between the smooth muscle in the urethral wall and the epithelial lining, the mucosal seal between the walls of the closed urethral lumen (coaptation), and support from endopelvic fascia. During urination the muscles in and around the urethra relax and the bladder muscle (the detrusor) contracts. Fluid pressure from the bladder overcomes the mucosal seal, the lumen opens and urine is expelled.
While the bladder is filling, increases in bladder pressure normally induce reflex reactions in the muscles of the continence system to increase urethral closure pressure. This reflex response is normally adequate to prevent involuntary urine loss. If the resistance to urethral opening is insufficient to keep the lumen sealed, the female patient experiences episodes of stress incontinence. Stress incontinence results from inadequate functioning of one or more of the components of the normal continence system.
Options currently available for management of female urinary stress incontinence include the use of externally applied absorbent products, pelvic muscle exercises, electrical stimulation of pelvic muscles, devices that occlude the urethra either internally or externally at the urethral meatus, and injections that add bulk to the urethral wall and surgery. A number of external and internal female continence devices have been patented.
U.S. Pat. No. 5,074,855 discloses a device for controlling urinary incontinence in a human female including a resilient pad configured to seal against and occlude the urethral meatus of the user. A similar device is disclosed in U.S. Pat. No. 5,336,208. In those devices, an adhesive is provided to seal the body of the device against the urethral meatus.
International Applications No. 96/39989, 96/39990 and 96/39991 each disclose a female urinary incontinence device in the form of an urethral cap with a partially deformable body portion, a hand gripping portion and a body contacting surface. The body portion defines a chamber which allows for a vacuum seal when applied to the patient's body.
U.S. Pat. No. 5,082,006 has a shaft to be inserted into the urethra and one or more knobs on the shaft to plug the passage of urine therethrough. A flap on the proximal end of the shaft holds the positioning of the shaft in the urethra.
Each of the above devices prevents urinary loss by occluding the internal or external urethral orifice and each has to be removed by the patient to allow micturition.
It is desirable to have a device which satisfactorily prevents urinary loss and also permits voluntary voiding without needing to remove the device from the body of the patient. It has now been found that these benefits may be achieved with a female continence augmentor that prevents involuntary urine loss while allowing urine flow during voluntary micturition. The female continence augmentor, described herein, achieves the desired effects by gently stretching and reshaping the midurethra from within its lumen. Stretching the perimeter of the lumen increases tension in the surrounding midurethral wall bringing the opposing surfaces of the epithelial lining into more intimate contact for enhancing coaptation. Coupled with the action of the regular continence mechanism, the increased tension and improved coaptation make the urethra more resistant to dilation by urine during transient increases in abdominal pressure, thus relieving stress incontinence.
When the user of the female continence augmentor wishes to void, the muscles of her continence mechanism relax, reducing tension in the urethral wall sufficiently to permit dilation of the lumen under normal bladder pressure. The female continence augmentor acts as a spring, exerting force directly proportional to the compressive force applied by the muscles of the continence mechanism. When the continence mechanism relaxes, the force from the augmentor drops to a level that does not significantly increase the fluid pressure required to dilate the urethra for urination. The female continence augmentor maintains contact with the dorsal midurethral wall at all times, but the reduced muscular tension allows urine pressure to stretch the urethra, opening a slit-shaped passage for urine between the ventral urethral wall and the ventral surface of the augmentor.
When voiding is complete, contraction of the sphincteric muscles restores tension in the urethral wall and the female continence augmentor resumes functioning automatically. Thus, the female continence augmentor functions through dynamic interactions with the biological continence mechanism. Its mode of action is clearly different than that of previous intraurethral continence devices, which act as plugs that must be removed or plugs with valves that must be externally activated for voiding.